Numerical Analysis of Influence on Gas Supply Hole Number and Radial Clearance for the Characteristics of Hydroinertia Gas Journal Bearings

Abstract

Hydroinertia gas journal bearings have been applied to solid state nuclear magnetic resonance spectroscopy. These bearings, which require a larger radial clearance than conventional externally pressurized bearings, achieve stable operation for ultra high-speed rotation of spinner shaft at several million rpm. However, their small diameters, which range within 1-6 mm, have limited experimental verifications of their static characteristics. A computational fluid dynamics analysis was therefore performed to fill this gap. The effects of radial clearance and gas supply hole number on bearing characteristics, such as pressure distribution and load capacity, were investigated. This analysis showed that negative and positive pressures generated some clearance. Pressure distribution also changes in the gas supply hole number. A large load capacity was obtained at this clearance. To verify the phenomenon, measurement of pressure distribution was performed using experimental setup. Negative pressure could be confirmed actually in the large radial clearance condition.